Earnings Per Share - Computation of Basic and Diluted Net Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Numerator:
Net income									$ 43,840	$ 20,945	$ 5,663
Less: income allocable to participating securities									(333)	(270)
Income allocable to common shares									43,507	20,675	5,663
Add back: undistributed earnings allocable to participating securities									333	270
Less: undistributed earnings reallocated to participating securities									(333)	(264)
Numerator for diluted earnings per share									$ 43,507	$ 20,681	$ 5,663
Denominator:
Weighted average common shares outstanding									50,315,455	50,315,455	49,002,809
Weighted average common shares repurchased									(286,699)
Adjustment for vested restricted stock									7,521,448	6,179,715	781,345
Shares for calculating basic earnings per share	57,652,531	57,819,734	57,591,556	57,132,909	57,109,987	57,050,684	57,038,021	54,749,951	57,550,204	56,495,170	49,784,154
Dilutive effect of unvested restricted stock									1,417,895	1,424,530	2,073,155
Shares for calculating diluted earnings per share	58,882,966	58,907,281	58,697,229	58,362,040	58,365,587	58,367,830	58,369,083	56,562,661	58,968,099	57,919,700	51,857,309
Earnings per share:
Basic	$ 0.15	$ 0.11	$ 0.18	$ 0.32	$ 0.09	$ 0.07	$ 0.10	$ 0.11	$ 0.76	$ 0.37	$ 0.11
Diluted	$ 0.15	$ 0.10	$ 0.18	$ 0.31	$ 0.09	$ 0.07	$ 0.10	$ 0.11	$ 0.74	$ 0.36	$ 0.11